"Split" air conditioning systems are those systems in which a first heat exchanger is located indoors while a second heat exchanger is located outdoors. The heat exchangers are connected in series with refrigerant traveling from a compressor, which is typically located outdoors, to either the indoor or the outdoor heat exchanger. In a dedicated air conditioning application refrigerant flows from the compressor to the outdoor heat exchanger coil, which functions as a condenser, and then indoors to the heat exchanger coil which functions as an evaporator.
In a heat pump circuit the refrigerant flows from the compressor to the one of the outdoor and indoor heat exchanger coils that operates as a condenser which, in turn, depends upon the mode of circuit operation. In any case, the performance of any split air conditioning or heat pump system is significantly affected by the flow of air through and over the system's outdoor heat exchanger.
The outdoor heat exchanger in a split system is typically enclosed in a cabinet which also houses (1) refrigeration system controls, (2) a refrigerant compressor, (3) refrigerant plumbing, and (4) a fan. The cabinet must afford protection for the components it houses from debris and the elements while allowing for sufficient airflow to promote the efficient transfer of heat between the refrigerant flowing through the outdoor heat exchanger and outdoor air. Such heat exchange is critical since in both indoor space heating and indoor space cooling operations outdoor air is the heat source or heat sink upon which system operation relies.
The design of outdoor heat exchanger cabinets has historically been a tradeoff between airflow and component protection considerations, among other things. Other considerations are component accessibility for maintenance and/or repair, cabinet drainage, noise quieting, cabinet appearance, air discharge direction and ease of fabrication.
Air conditioning outdoor sections most commonly draw air over the heat exchanger housed therein through the sides or periphery of their cabinets. Such air, after passing through the heat exchanger, is typically discharged upward and away from the cabinet through the cabinet top. One very significant reason for discharging the air upward to a location remote from the location where air is drawn into the heat exchanger is to prevent the mixing of air which has just traveled through the heat exchanger with air being initially drawn into the heat exchanger. If such mixing is allowed to occur the heat exchange efficiency of the outdoor heat exchanger is significantly reduced. Typical of this configuration are the outdoor heat exchanger cabinets illustrated in U.S. Pat. Nos. 4,036,292 and 4,307,778. A disadvantage of this type of outdoor section configuration is the exposure of the components interior of the cabinet to debris such as twigs and leaves which can fall into the cabinet between the louvers of the cabinet top. Such cabinets also directly expose the components interior thereof to hail, rain, sleet and snow. If the louvers are spaced too far apart, the ability of debris to fall into the cabinet increases while if the louvers are too close, airflow efficiency suffers.
A different outdoor cabinet configuration is found in U.S. Pat. No. 3,759,321 in which air is both drawn into and discharged from the sides of an outdoor cabinet. While this design is somewhat protective of the components interior of it, it is conducive to the recirculation of discharged air with air being drawn into the cabinet because of the proximate locations of air entry into and discharge from the cabinet. As noted above, such recirculation diminishes the efficiency of the heat exchange process significantly. Further, the horizontal direction of air discharge is disadvantageous from the standpoint that air conditioning outdoor units are generally located at the side of a residence or building in a landscaped area. The velocity and volume of air discharged from an outdoor cabinet is typically significant and can damage bushes, flowers and the like in the near vicinity of the cabinet.